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Tekcem Standard screed cement
- 1. Tekcem Standard SETTING NEW LEVELS www.tekcem.co.uk The Screed Development Centre Unit5 The Business Centre, Barlow Drive, Winsford, Cheshire CW7 2GN Sales: 03300 555 227 Technical: 03300 553 714 OVERVIEW Tekcem is a cement based binder to replace Ordinary Portland Cement where improved strength and drying performance is required. Tekcem must be combined with suitable aggregates and water using exactly the same methods as for mixing a normal (unimproved) sand / cement screed mortar. For further improvement of overall performance of Tekcem, proprietary construction fibres may be added or can be supplied preblended. BENEFITS - Quickerdryingenablingearlierapplicationof floorcoverings. - Canbelightlytraffickedafter12hours. - ProvidesscreedstoISCRCatAorB depending onmixdesign. - Canbesuppliedwithfibresforgreatercontrol ofcracking. - Suitableforallnormalscreedapplications includingoverunderfloorheating. TECHNICAL DATA COVERAGE Tekcem is a special cementitious binder designed to replace OPC in traditional sand / cement screed to enable early foot trafficking and provide quicker drying. Tekcem is used to produce bonded, unbonded and floating screeds in internal situations including over underfloor heating. Packaging 20kg lined paper sacks Appearance Grey, cementitious powder Typical Screed Properties Fully compacted dry screed density 1900 - 2100kg/m² ISCR Soundness to BS8204-1 Cat A or Cat B Light foot traffic 24 hours Full traffic 7 days Drying time 7 days per 25mm under good drying conditions TYPICAL SCREED MIX DESIGN Screed type Composition Approx yield ISCR Cat A 100kg Tekcem, 360kg screeding sand (1:3 volume mix) 0.25m³ ISCR Cat B 100kg Tekcem, 500kg screeding sand (1:4 volume mix) 0.3m³ Coverage per 100kg of Tekcem Standard Applied thickness Approx. coverage at 1:3 Approx. coverage at 1:4 40mm 5.8m² 7.5m² 50mm 4.6m² 6.0m² 60mm 3.8m² 5.0m² 75mm 3.1m² 4.0m²
- 2. Tekcem Standard SETTING NEW LEVELS www.tekcem.co.uk The Screed Development Centre Unit5 The Business Centre, Barlow Drive, Winsford, Cheshire CW7 2GN Sales: 03300 555 227 Technical: 03300 553 714 SCREED SYSTEMS Tekcem modified screeds can be applied in bonded, unbonded and floating construction configurations. Bonded screeds should be laid at thicknesses of 25 - 40mm. Bonded screeds should use a suitably applied sealer and slurry bonding coat or specific bonding agent as required. It is possible to install Tekcem modified screeds at thicknesses down to 15mm by careful selection of aggregate and use of using specific bonding agents. Unbonded screeds should be applied over a suitable damp proof or separating membrane at a minimum thickness of 40mm. Floating screeds should use a suitable membrane to separate the screed from the underlying insulation and should be at a minimum thickness of 75mm or 65mm for domestic applications. Thicknesses can be reduced to 55mm over rigid insulation board. Cover to underfloor conduits or heating pipes should be a minimum of 25mm. Partially bonded screeds, with no separating membrane or bonding agent used, often result in cracking and should be avoided. All unbonded and floating screeds are to be reinforced and may be reinforced with proprietary construction fibres or alternatively Tekcem can be supplied preblended with fibres. TOOLS REQUIRED Screed - Forced action mixer - Screed bar - Plastic float - Steel float Wash all tools thoroughly with water directly after use. SURFACE PREPARATION Before starting, all substrates must be sound, clean and dry. The substrate surface should be reasonably flat and true as sudden level changes may lead to sudden changes in screed thickness and should be avoided as they can induce cracking. For bonded screeds, mechanically remove all laitance, dust, dirt, oil, grease and other contaminants that may affect adhesion. Heavily contaminated floors may require special treatment. Sub- floors directly to earth must have a DPM. If there is no DPM present or the surface relative humidity is above 75%RH the application of a combined DPM and bonding agent directly beneath the screed will facilitate the drying of the screed. SUBSTRATES Concrete/screed: The strength of the substrate should be compatible with the stresses associated with application and hardening of the screed. For bonded construction it is preferable that the compressive strength of the substrate is a minimum of 25MPa. Additionally for bonded screeds, it is necessary to apply a sealer coat and then prime the substrate with a Tekcem slurry bonding coat or to employ specific bonding agents prior to the application of the screed. MIXING Tekcem modified screeds should be mixed in a forced action mixer. Pre-mix suitable fine aggregate and Tekcem. Add water to give the required consistency. Mix thoroughly for 3 mins. Semi-dry consistency is judged as the consistency at which it is possible to make a ball of the material in the hand, which will retain its shape but will not easily yield “free” water when squeezed. Care should be taken not to overwater the screed as this will increase drying time and lead to surface bleed. Remember to take into account of any water content of the aggregate. The mix has a working life of approximately 45 - 60 minutes. APPLICATION The applied screed is consolidated and levelled by tamping with a screed bar and rubbing with a plastic float. A smooth finish is achieved by light trowelling with a steel trowel. The screed should be laid at a maximum depth of 75mm. If greater depths are required, this may be carried out by building up in roughly two equal layers with the surface of the intermediate layer being scratch-keyed before applying the second layer. Each layer is to be compacted separately and applied within 30 minutes to ensure a monolithic total thickness. The screed should be cured, ideally under polythene, as soon as practicable after application for a minimum of 7 days, after which drying should be allowed to occur naturally. The screed should not be force dried or exposed to severe drying conditions. It is the responsibility of the floor finishes applicator to ensure that the residual moisture in the screed is suitably low prior to any floor finishes being laid. Underfloor heating: Underfloor heating can be gradually introduced once the screed is fully cured (min 7 days) and the surface relative humidity has dried to 75%RH or below. Start with a low temperature, gradually increasing the temperature (eg by 2°C per day) over a 2 week period. LIMITATIONS The application of Tekcem modified screeds, sealer and slurry bonding coats should only be carried out when the floor temperature is 5 - 30°C and the ambient relative humidity is below 75%. These conditions should be maintained during application and drying. Consideration should be given to the isolation of walls and columns or similar and to the forming/cutting of movement or day joints. WARNING The information provided in this datasheet corresponds to the best of our expert knowledge and experience. Whilst it is true and accurate to the best of our knowledge, it may contain information which is unsuitable under certain circumstances since materials, site conditions and method of application vary with each application. Tekcem Ltd cannot be held be responsible for any loss or damage due to incorrect use or from the possibility of variations in working conditions and/or workmanship beyond our control. The user alone is responsible for any consequences deriving from the product. HEALTH AND SAFETY This product is not classified under the Chemicals Hazard Information and Packaging for Supply Regulations. A Material Safety Data Sheet relating to this product can be obtained from Tekcem Ltd. Please dispose of packaging and waste responsibly. ;STORAGEANDSHELFLIFE Six months in unopened bags and stored under good, cool and dry conditions.